64 ENTOMOLOGY 
make one; and, in any case, may be determined graphically by 
means of a kymograph, which, in one of its forms consists of 
a cylinder covered with smoked paper and revolved by clock- 
work at a uniform rate. The insect is held in such a position 
that each stroke of the wing makes a record on the smoked 
paper, as in Fig. 74. Comparing this record with one made 
Fic. 74. 
VV NWN ONAN CURA aah eC ON NDE wees uve AN ativan aaAnsansaasans: 
Records of wing vibration. A, mosquito, Anopheles. Above is the wing record 
and below is the record of a tuning fork which vibrated 264.6 times per second. B, 
wasp, Polistes. The tuning fork in this instance had a vibration frequency of 97.6. 
on the same paper by a tuning fork of known vibration period, 
the frequency of wing vibration can be determined with great 
accuracy. As the wing moves in the arc of a circle, the radius 
of which is the length of the wing, the extreme tip of the wing 
records only a short mark; if, however, the wing 1s pressed 
against the smoked cylinder, a large part of the figure 8 trajec- 
tory may be obtained, as in Fig. 74, B. The wings of the two 
sides move synchronously, as Marey found. 
The smaller the wings are, the more rapidly they vibrate. 
Thus a butterfly (P. rape) makes 9 strokes per second, a 
dragon fly 28, a sphingid moth 72, a bee I90 and a house 
fly 330. 
Wing Muscles.—The base of a wing projects into the 
thoracic cavity and serves for the insertion of the direct mus- 
cles of flight. Regarding the wing as a lever (Fig. 75, 4), 
